Subclinical hypothyroidism (SH) is biochemically defined as serum TSH levels above the upper limit of the reference range in the presence of normal free T4 (FT4) concentrations. While there is a general agreement to treat subjects with serum TSH levels above 10 mU/L, the management of mild form (TSH concentrations between 4.5 and 10 mU/L) is still a matter of debate. In children, mild SH is often a benign and remitting condition and the risk of progression to overt thyroid dysfunction depends on the underlying condition, being higher in the autoimmune forms. The major concern is to establish whether SH in children should always be considered an expression of mild thyroid dysfunction and may deserve treatment. Current data indicate that children with mild SH have normal linear growth, bone health and intellectual outcome. However, slight metabolic abnormalities and subtle deficits in specific cognitive domains have been reported in children with modest elevation of TSH concentration. Although these findings are not sufficient to recommend levothyroxine treatment for all children with mild SH, they indicate the need for regular monitoring to ensure early identification of children who may benefit from treatment. In the meanwhile, the decision to initiate therapy in children with mild SH should be based on individual factors.
Mariacarolina Salerno, Nicola Improda and Donatella Capalbo
Malgorzata Wasniewska, Tommaso Aversa, Mariacarolina Salerno, Andrea Corrias, Maria Francesca Messina, Alessandro Mussa, Donatella Capalbo, Filippo De Luca and Mariella Valenzise
To follow-up for 5 years thyroid status evolution in 127 girls with mild (TSH 5–10 mU/l) subclinical hypothyroidism (SH) of different etiologies.
The population was divided into two age-matched groups of 42 and 85 girls with either idiopathic (group A) or Hashimoto's thyroiditis (HT)-related SH (group B). Group B was in turn divided into three subgroups, according to whether SH was either isolated or associated with Turner syndrome (TS) or Down syndrome (DS).
At the end of follow-up the rate of girls who became euthyroid was higher in group A (61.9% vs 10.6%), whereas the rates of patients who remained SH (55.3% vs 26.2%), became overtly hypothyroid (30.6% vs 11.9%) or required levothyroxine (l-T4) therapy (63.5% vs 23.8%) were higher in group B. Among the girls of group B, the risk of remaining SH or developing overt hypothyroidism was higher in the subgroups with TS or DS than in those with isolated HT.
Long-term prognosis of mild and idiopathic SH is frequently benign, even though a l-T4 treatment may be needed throughout follow-up in almost a quarter of cases; long-term prognosis is different in the girls with either idiopathic or HT-related SH; and the association with either TS or DS impairs the outcome of HT-related SH.
Manuela Cerbone, Donatella Capalbo, Malgorzata Wasniewska, Sara Alfano, Giuseppina Mattace Raso, Ugo Oliviero, Antonio Cittadini, Filippo De Luca and Mariacarolina Salerno
To investigate the effect of levothyroxine (L-T4) treatment on early markers of atherosclerotic disease in children with mild idiopathic subclinical hypothyroidism (SH).
Two-year, open, case–control prospective study.
A total of 39 children, aged 9.18±3.56 years, with SH and 39 healthy controls were enrolled in the study. Waist-to-height ratio (WHtR), blood pressure, triglycerides, total cholesterol (total-C), HDL-C, LDL-C, non-HDL-C, triglycerides/HDL-C, atherogenic index (AI), homocysteine (Hcy), asymmetric dimethylarginine (ADMA), flow-mediated dilation (FMD) and intima–media thickness (IMT) were evaluated at baseline and after 2 years of L-T4 treatment in SH children and after 2 years of follow-up in controls.
At study entry WHtR was higher in SH subjects compared with controls (0.56±0.08 vs 0.49±0.07, P=0.04) and significantly decreased after 2 years of treatment (0.50±0.06, P<0.0001). Mean HDL-C levels (50.47±11.43 vs 61.06±13.83mg/dL, P=0.002) were lower, while triglycerides/HDL-C (1.63±1.07 vs 1.19±0.69, P=0.05), AI (3.32±0.90 vs 2.78±0.68, P=0.005), and Hcy (9.35±2.61 vs 7.71±1.94μmol/L, P=0.01) were higher in SH subjects compared with controls and improved after 2 years of treatment (HDL-C 56.26±13.76mg/dL, P<0.0001; triglycerides/HDL-C 1.23±0.78, P=0.006; AI 2.82±0.68, P<0.0001; and Hcy 8.25±2.09μmol/L, P=0.06). ADMA concentrations at baseline were higher in SH subjects compared with controls (0.77±0.21 vs 0.60±0.16μmol/L, P=0.001) and decreased after therapy (0.58±0.13μmol/L, P<0.0001). FMD, IMT and other metabolic parameters were not different among SH subjects and controls at baseline and after 2 years.
Children with SH may have subtle pro-atherogenic abnormalities. Although L-T4 treatment exerts some beneficial effects, the long-term impact of therapy on metabolic outcomes in SH children still remains unclear.
Ugo Oliviero, Antonio Cittadini, Giorgio Bosso, Manuela Cerbone, Antonio Valvano, Donatella Capalbo, Valentina Apuzzi, Fabrizia Calabrese, Teresa Lettiero and Mariacarolina Salerno
Patients with congenital hypothyroidism (CH) display subclinical abnormalities of the cardiovascular system that are related to unphysiological fluctuations of TSH levels and occur despite careful replacement therapy.
The aim of the present case–control study was to evaluate the effects of long-term levothyroxine (l-T4) replacement therapy on the vascular district in CH patients by assessing endothelial function with flow-mediated dilation (FMD) and brachial artery distensibility with the measurement of the coefficient of distensibility (DC).
Thirty-two young adults with CH aged 18.9±0.2 years and 32 age- and sex-matched controls underwent brachial Doppler ultrasound examination to measure FMD and DC at the time of the study. Hypothyroidism was diagnosed by neonatal screening, and l-T4 treatment was initiated within the first month of life.
Compared to healthy controls, CH patients had significantly reduced brachial artery reactivity with lower FMD values (8.9±5.7 vs 14.1±5.1% P=0.003) and decreased vascular distensibility (24.6±1.6 vs 27.3±3 kPa−1×10−3, P<0.0002). Linear regression analysis revealed that both total and pubertal mean TSH and number of episodes of undertreatment were independent determinants of FMD and DC. Pubertal mean TSH was the best predictor of both FMD and DC (r=0.81 and r=0.87 respectively, P<0.001).
Young adults with CH treated with long-term l-T4 replacement therapy may have significant impairment of both FMD and DC. Our data suggest that high TSH levels, inadequately corrected by l-T4 replacement therapy in CH patients especially during puberty, can exert significant effects on the elastic and functional vessel properties.
Malgorzata Wasniewska, Mariacarolina Salerno, Alessandra Cassio, Andrea Corrias, Tommaso Aversa, Giuseppina Zirilli, Donatella Capalbo, Milva Bal, Alessandro Mussa and Filippo De Luca
To prospectively evaluate the course of subclinical hypothyroidism (SH) in children and adolescents with no underlying diseases and no risk factors, which might interfere with the progression of SH.
Clinical status, thyroid function, and autoimmunity were prospectively evaluated at entry and after 6, 12, and 24 months in 92 young patients (mean age 8.1±3.0 years) with idiopathic SH.
During the study, mean TSH levels showed a trend toward a progressive decrease while FT4 levels remained unchanged. Overall, 38 patients normalized their TSH (group A): 16 patients between 6 and 12 months, and 22 patients between 12 and 24 months. Among the remaining 54 patients, the majority maintained TSH within the baseline values (group B), whereas 11 exhibited a further increase in TSH above 10 mU/l (group C). Baseline TSH and FT4 levels were similar in the patients who normalized TSH, compared with those with persistent hyperthyrotropinemia. Even in the patients of group C, both TSH and FT4 at entry were not different with respect to those of groups A and B. No patients showed any symptoms of hypothyroidism during follow-up and no changes in both height and body mass index were observed throughout the observation period.
(a) The natural course of TSH values in a pediatric population with idiopathic SH is characterized by a progressive decrease over time; (b) the majority of patients (88%) normalized or maintained unchanged their TSH; and (c) TSH changes were not associated with either FT4 values or clinical status or auxological parameters.
Manuela Cerbone, Carmela Bravaccio, Donatella Capalbo, Miriam Polizzi, Malgorazata Wasniewska, Daniela Cioffi, Nicola Improda, Mariella Valenzise, Dario Bruzzese, Filippo De Luca and Mariacarolina Salerno
The treatment of children with subclinical hypothyroidism (SH) is controversial for TSH values between 4.5 and 10 mU/l. The aim of this cross-sectional, controlled study was to evaluate growth and intellectual outcome in children with persistent SH who have never been treated with levothyroxine.
Design and methods
Clinical and auxological parameters, thyroid function, and intellectual outcome were evaluated in 36 children with persistent SH at the age of 9.7±0.6 (range 4–18.0) years. Children had been followed longitudinally for 3.3±0.3 (range 2.0–9.3) years, from first diagnosis of SH until enrollment in the study. Thirty-six age- and sex-matched children were enrolled in the study as controls.
At study entry, height (−0.8±0.2 SDS), bone age/chronological age (BA/CA ratio 0.92±0.6), and body mass index (BMI −0.1±0.2 SDS) in SH children were normal. Despite long-term duration of SH, none of these parameters showed a worsening with respect to height (−0.7±0.2 SDS), BA/CA (0.97±0.03), and BMI (−0.1±0.2) at the time of first SH detection. None of the children showed overt signs or symptoms of hypothyroidism during the follow-up.
Verbal (99.1±2.2), performance (100.4±1.9), and full-scale (99.7±1.9) intelligence quotient (IQ) scores in SH children were normal and comparable to those of controls. No relationship was detected between IQ scores and the degree or duration of SH.
Persistent SH in children is not associated with alterations in growth, bone maturation, BMI, and cognitive function or other complaints that could be ascribed to SH even after several years without therapeutic intervention.